Queen's University

About: Queen's University is a education organization based out in Kingston, Ontario, Canada. It is known for research contribution in the topics: Population & Poison control. The organization has 41065 authors who have published 78811 publications receiving 2864794 citations. The organization is also known as: Queen's College at Kingston.

The orbifold Chow ring of toric Deligne-Mumford stacks

Abstract: The orbifold Chow ring of a Deligne-Mumford stack, defined by Abramovich, Graber and Vistoli [2], is the algebraic version of the orbifold cohomology ring in troduced by W. Chen and Ruan [7], [8]. By design, this ring incorporates numerical invariants, such as the orbifold Euler characteristic and the orbifold Hodge num bers, of the underlying variety. The product structure is induced by the degree zero part of the quantum product; in particular, it involves Gromov-Witten invariants. Inspired by string theory and results in Batyrev [3] and Yasuda [28], one expects that, in nice situations, the orbifold Chow ring coincides with the Chow ring of a resolution of singularities. Fantechi and G?ttsche [14] and Uribe [25] verify this conjecture when the orbifold is Symn(5) where 5 is a smooth projective surface with Ks = 0 and the resolution is Hilbn(?>). The initial motivation for this project was to compare the orbifold Chow ring of a simplicial toric variety with the Chow ring of a cr?pant resolution. To achieve this goal, we first develop the theory of toric Deligne-Mumford stacks. Modeled on simplicial toric varieties, a toric Deligne-Mumford stack corresponds to a combinatorial object called a stacky fan. As a first approximation, this object is a simplicial fan with a distinguished lattice point on each ray in the fan. More precisely, a stacky fan S is a triple consisting of a finitely generated abelian group N, a simplicial fan E in Q z N with n rays, and a map ?: Zn ?> N where the image of the standard basis in Zn generates the rays in E. A rational simplicial fan E produces a canonical stacky fan S := (N, E, ?) where N is the distinguished lattice and ? is the map defined by the minimal lattice points on the rays. Hence, there is a natural toric Deligne-Mumford stack associated to every simplicial toric variety. A stacky fan ? encodes a group action on a quasi-affine variety and the toric Deligne-Mumford stack #(?) is the quotient. If E corresponds to a smooth toric variety X?E) and S is the canonical stacky fan associated to E, then we simply have #(!?) = X?Z). We show that many of the basic concepts, such as open and closed toric substacks, line bundles, and maps between toric Deligne Mumford stacks, correspond to combinatorial notions. We expect that many more results about toric varieties lift to the realm of stacks and hope that toric Deligne Mumford stacks will serve as a useful testing ground for general theories.

Unlocking the full potential of organic light-emitting diodes on flexible plastic

Abstract: Using a thin-film outcoupling enhancement method consisting of a weak optical cavity on a flexible substrate with a non-indium-tin-oxide anode, researchers demonstrate phosphorescent organic LEDs with an external quantum efficiency of up to 63% at green wavelengths, which remains as high as 60% at luminous intensities of >10,000 cd m−2.

Varus and valgus alignment and incident and progressive knee osteoarthritis

Abstract: Objective Varus and valgus alignment increase medial and lateral tibiofemoral load. Alignment was associated with tibiofemoral osteoarthritis progression in previous studies; an effect on incident osteoarthritis risk is less certain. This study tested whether alignment influences the risk of incident and progressive radiographic tibiofemoral osteoarthritis. Methods In an observational, longitudinal study of the Multicenter Osteoarthritis Study cohort, full-limb x-rays to measure alignment were acquired at baseline and knee x-rays were acquired at baseline and knee x-rays at baseline and 30 months. Varus alignment was defined as ≤178° and valgus ≥182°. Using logistic regression and generalised estimating equations, the associations of baseline alignment and incident osteoarthritis at 30 months (in knees without baseline osteoarthritis) and alignment and osteoarthritis progression (in knees with osteoarthritis) were examined, adjusting. For age, gender, body mass index, injury, laxity and strength, with neutral knees as referent. Results 2958 knees (1752 participants) were without osteoarthritis at baseline. Varus (adjusted OR 1.49, 95% CI 1.06 to 2.10) but not valgus alignment was associated with incident osteoarthritis. 1307 knees (950 participants) had osteoarthritis at baseline. Varus alignment was associated with a greater risk of medial osteoarthritis progression (adjusted OR 3.59, 95% CI 2.62 to 4.92) and a reduced risk of lateral progression, and valgus with a greater risk of lateral progression (adjusted OR 4.85, 95% CI 3.17 to 7.42) and a reduced risk of medial progression. Conclusion Varus but not valgus alignment increased the risk of incident tibiofemoral osteoarthritis. In knees with osteoarthritis, varus and valgus alignment each increased the risk of progression in the biomechanically stressed compartment.

Handoffs in fourth generation heterogeneous networks

Abstract: As mobile wireless networks increase in popularity and pervasiveness, we are faced with the challenge of combining a diverse number of wireless networks. The fourth generation of wireless communications is expected to integrate a potentially large number of heterogeneous wireless technologies in what could be considered a huge step forward toward universal seamless access. One of the main challenges for seamless mobility is the availability of reliable horizontal (intrasystem) and vertical (intersystem) handoff schemes. Efficient handoff schemes enhance quality of service and provide flawless mobility. This article presents different and novel aspects of handoff and discusses handoff related issues of fourth generation systems. Desirable handoff features are presented. Handoff decisions, radio link transfer, and channel assignment are described as stages of the complete handoff process. A vertical handoff decision function, which enables devices to assign weights to different network parameters, is also presented